1. Field of the Invention
The present invention relates to an adaptor for multi-channel pipettors which allows for the use of gel-loading tips to simultaneously load multiple wells of a gel.
2. Related Art
Pipettors are used in laboratories to transfer small amounts of liquids (generally 1 ml or less) from one receptacle to another. In recent years the development of multi-channel pipettors, as shown, for example, in U.S. Pat. No. 4,824,642, has allowed for the simultaneous transfer of multiple samples. Because of the fixed spacing between the channels, the transfer of liquids must be made from one set of receptacles to another set of identically spaced receptacles. When it is necessary to transfer liquid from one set of receptacles to another set of receptacles with different spacing it becomes necessary to use a single channel pipettor. The individual transfer of many different samples using a single channel pipettor is a time consuming process.
This can be especially tedious when transferring liquid from receptacles, such as those of a 96 well plate. These plates are heavily used in assays, such as PCR amplification, sequencing, etc. Current technology allows for high volume sample preparation (i.e. the use of multi-channel pipettors to transfer multiple samples from multiple tubes). However, sample analysis in agarose/acrylamide gels still requires individual loading of each sample. Most multi-channel pipettors are configured to match the spacing of the wells on 96 well plates, but this spacing is different than the spacings generally used for the wells of acrylamide and agarose gels. Therefore, the transfer of samples from 96 well plates to acrylamide or agarose gels using a multi-channel pipettor is not possible. These samples must be loaded one at a time into the wells of acrylamide or agarose gels, thereby greatly increasing the time and effort needed to perform research (e.g. sequencing, restriction digest analysis, genetic typing, etc.).
Acrylamide gels are polymerized between two glass plates which are separated by thin spacers on the side. Wells are made by inserting a thin comb at the top of the gel between the two plates before the acrylamide has set. These wells are loaded by pipetting the fluid into the well, being careful not to let the fluid seep into neighboring wells. Agarose gels, on the other hand, are cast in a gel-caster and, again, a comb is placed in the gel to form wells before the agarose is set. Once the agarose is set, it is placed in a gel electrophoresis apparatus filled with buffer and the comb is removed. Depending on the number of wells cast in the agarose, the loading of the samples is tedious and can result in errors if single channel pipetting devices are used.
Standard pipette tips are relatively rigid and wide and are difficult to use when loading acrylamide and agarose gels, which often times have narrow wells. Special tips for loading gels, as shown, for example, in U.S. Pat. No. 4,707,337, are much longer and more flexible than standard pipette tips. They also have a much thinner tip which allows them to load samples into narrow wells much more accurately. These tips are thin enough to fit in between the plates of a vertical gel and, thus, fluid can be delivered directly into the well, rather than from on top of the well with the fluid having to seep in between the two plates. Loading the fluid directly into the well greatly reduces the chances of the fluid seeping into neighboring wells.
In U.S. Pat. No. 5,061,449 and in U.S. Pat. No. 5,057,281, multi-channel pipettors capable of changing the spacing of the channels are described. These multi-channel pipettors contain 6 channels capable of being variably adjusted from being evenly spaced to being unevenly spaced apart. Adjusting these channels every time samples are transferred is very time consuming, especially if one transfers 96 samples from a 96 well plate to other differently spaced receptacles (this requires adjusting the channels 31 times--sixteen times to match the spacing of the receptacles to which the samples are transferred, and 15 times to match the spacing of the 96 well plates). Furthermore, the channels of these adjustable multi-channel pipettors can not be adjusted to match a narrow spacing, such as the spacings between the wells of acrylamide gels. In addition, it is difficult to use gel-loading tips on these pipettors to deliver the samples with any accuracy due to the flexibility and length of the gel-loading tips.
Therefore, there is a need in the art for a device that allows one to simultaneously load multiple wells of a gel in which the spacing of the wells is different (or variable) from the available spacing on the multi-channel pipettors. As the requirement increases for denser loading arrays on gels (vertical, substantially vertical, horizontal, or substantially horizontal) there is a need for devices which can adjust spacing from 96 well microtiter plates to the required spacing in gels. The spacing between the wells of these gels depends on the combs used. Many combs that are commercially available provide variable well size and spacing. Thus, using a single comb, one might have four wells capable of holding only 50 .mu.l of fluid and four wells capable of holding 0.5 ml of fluid. The present invention fulfills this need by allowing one to use multi-channel pipettors currently found in most laboratories to simultaneously load multiple wells of a gel using gel-loading tips. Multi-channel pipettors can cost hundreds of dollars. The prior art requires one to purchase new adjustable multi-channel pipettors, even though one might have a standard multi-channel pipettor at their disposal. Alternatively, the present invention costs a fraction of what a multi-channel pipettor costs. Thus, the present invention provides an inexpensive alternative to the prior art because it does not require the purchase of an expensive adjustable multi-channel pipettor.